Electrical Inductance Unit Converter

How to use this calculator

Inductance value — Enter the number. The converter in the screenshot above shows 100 µH converting to 0.1 mH, with the output panel showing all four units: 0.0001 H / 0.1 mH / 100 µH / 100,000 nH.

From unit — Pick your starting unit from the dropdown: Henry, Millihenry, Microhenry, Nanohenry.

To unit — The unit you want the primary result in.

The output panel shows the converted result large, with all four reference units below it. One input gives you the complete picture without running the converter four times.

The conversion formula

All inductance units are metric and all powers of 1,000. The henry is the base unit.

1 henry = 1,000 millihenries 1 millihenry = 1,000 microhenries 1 microhenry = 1,000 nanohenries 1 henry = 1,000,000,000 nanohenries (10⁹)

Going from a larger unit to a smaller one: multiply by 1,000 per step. Going from a smaller unit to a larger one: divide by 1,000 per step.

nH to µH: divide by 1,000. µH to mH: divide by 1,000. mH to H: divide by 1,000. The chain always works the same way.

Full unit reference table

The range from nanohenries to henries is 9 orders of magnitude. A surface-mount RF inductor on a smartphone PCB might be 2.2 nH. A toroidal power inductor in a desktop PC power supply is around 4.7 µH to 47 µH. An audio output transformer could be 5 H. These are not the same class of component at all, even though they’re all called “inductors.”

Common conversions at a glance

The pairs you’ll use most often in practice: µH to mH (÷1,000) when comparing a switching supply inductor to a filter spec, and nH to µH (÷1,000) when an RF chip datasheet gives a value in nH and your design tool wants µH.

Where inductance actually lives in a circuit

Inductance is a coil’s ability to store energy in a magnetic field and resist changes in current. When current through an inductor changes, the magnetic field changes, which induces a voltage that opposes the change. That property, resisting changes in current, is what makes inductors useful.

The key relationship:

V = L × (dI/dt)

Where V is the induced voltage, L is inductance in henries, and dI/dt is the rate of change of current in amperes per second. A larger inductor resists current changes more strongly for the same applied voltage. A 10 µH inductor builds current faster than a 100 µH inductor at the same voltage.

In a switching power supply operating at 500 kHz, the inductor charges and discharges 500,000 times per second. The inductance value controls how much the current rises and falls during each cycle (this is called “ripple current”). Too small an inductance: ripple is high and efficiency drops. Too large: the inductor is physically huge and the transient response is slow. The converter lets you compare inductor specs across datasheets that might quote the value in µH, mH, or the occasional nH for very small high-frequency designs.

Inductance scale: what values live where

The table below maps inductance ranges to the real world. These are rough but useful anchors.

Two things stand out. First: PCB trace inductance is real. A straight trace on a PCB has roughly 1 nH per millimeter of length. At 1 GHz, even a 10 mm trace (10 nH) is no longer just a wire; it’s an RF component with meaningful reactance. High-speed digital design takes this seriously.

Second: the “coil size reference diagram” mentioned in the tool’s subtitle matters because inductance scales with the square of the number of turns. Double the turns: quadruple the inductance. This means small nH inductors are tiny (sometimes 2 mm × 1.6 mm chip inductors), and large H-range inductors are physically substantial (toroidal cores the size of a fist or larger).

Real-world examples

Switching power supply: inductor selection

A buck converter steps 12V down to 5V at 2A load. Operating frequency is 300 kHz. The designer calculates the required inductance using the inductor ripple current equation:

L = (Vin - Vout) × Vout / (Vin × f × ΔIL)

Where ΔIL is the target ripple current (typically 20-40% of max load current).

RF filter: matching nH specs to simulation tools

An LC low-pass filter for a 433 MHz ISM band transmitter uses a 15 nH inductor. The simulation tool’s component library lists inductors in µH.

Audio crossover: converting speaker component specs

A 2-way speaker crossover splits audio frequencies at 3,000 Hz. The tweeter low-pass filter requires a series inductor. The calculated value is 2.65 mH.

Ferrite bead: nH and its role as a noise filter

Ferrite beads are technically inductors, but they’re used as frequency-dependent resistors. At low frequencies they pass current; at high frequencies they absorb noise as heat. Their inductance is typically specified in nH or µH.

A ferrite bead rated 600 Ω at 100 MHz with 100 nH inductance is placed in series with a power supply line to filter switching noise.

Transformer: millihenries to henries

A small 50 Hz audio output transformer has a primary inductance of 8 H. A datasheet for a competing part lists it as 8,000 mH.

Inductive reactance: why the frequency matters

Inductance on its own is a physical property of a coil. Inductive reactance is what that coil does in a circuit at a specific frequency.

XL = 2π × f × L

Where XL is reactance in ohms, f is frequency in Hz, and L is inductance in henries.

The same 100 µH inductor behaves very differently at different frequencies:

At 60 Hz, 100 µH is essentially a wire. At 100 MHz, it’s a 62.8 kΩ block. The component doesn’t change; the frequency does.

This is why RF inductors are tiny (nH range). At 2.4 GHz (Wi-Fi), a 1 nH inductor already has about 15 Ω of reactance. A 1 µH inductor at that frequency would have 15,080 Ω of reactance, which is useless for most RF circuits.

And it’s why power supply inductors are larger (µH range). At 300 kHz, you need enough inductance to meaningfully limit ripple current. Too small an inductance and the ripple current is unacceptably high.

When you convert inductance values and see a result that feels wrong, check what frequency domain the application is in. An RF engineer seeing “2.2 nH” thinks small but reasonable. A power supply engineer seeing the same number should convert: 2.2 nH is 0.0022 µH, which is comically small for a DC-DC converter and would result in extremely high ripple current.

The self-resonant frequency problem

Real inductors aren’t pure inductors. They have:

• Inductance (the useful property)
• DC resistance (the wire’s resistance)
• Parasitic capacitance (between turns of the winding)

That parasitic capacitance forms an LC circuit with the inductance itself. At a certain frequency, the inductor self-resonates. Above that frequency, it behaves as a capacitor.

This is the self-resonant frequency (SRF), and it’s listed on inductor datasheets.

A 100 µH inductor with an SRF of 5 MHz is only useful as an inductor below about 5 MHz. Above that, it’s capacitive. For a 300 kHz switching supply, this is fine. For a 10 MHz RF circuit, this particular 100 µH inductor is the wrong part.

The pattern: smaller inductors have higher SRF, which is why they’re used in RF applications. Larger inductors have lower SRF, which is fine for power and audio applications that don’t approach those frequencies.

When you’re using the converter and comparing inductors across datasheets, the inductance value alone doesn’t tell the whole story. SRF and DCR matter too. The conversion gets you a consistent unit to compare; the datasheet gives you the rest.

Where unit confusion costs you

Wrong frequency domain. A designer familiar with audio equipment (mH range) picks a 10 mH inductor for an RF filter application that needs 10 nH. That’s a factor of 1,000,000 off. The circuit won’t work and the failure mode might not be obvious without probing the board.

nH vs µH in simulation. A simulation tool prompts for inductance in µH. The datasheet gives 470 nH. Typing “470” into a µH field gives 470 µH, which is 1,000 times the intended value. The simulation runs fine because simulations run regardless of whether the input is sensible, and the resulting filter cutoff will be at a completely wrong frequency.

mH vs H on transformer datasheets. A power transformer spec sheet lists primary inductance as 500 mH. A calculation elsewhere in the design uses H. Plugging in 500 instead of 0.5 gives a magnetizing reactance 1,000 times too high, which makes the no-load current look negligible when it’s actually significant.

Ferrite bead inductance vs filter inductance. Some engineers grab a ferrite bead when they need a filter inductor because ferrite beads are cheap and available. Ferrite beads and inductors have similar nH-to-µH ranges, but ferrite beads are lossy by design. Their impedance is a complex mix of resistance and reactance, not pure inductance. Using the inductance value from a ferrite bead spec in an LC filter calculation gives you wrong cutoff frequencies because the model is wrong, not the unit conversion.

Coil geometry and inductance: the physical side

The converter outputs numbers. The physical inductor behind those numbers has geometry that determines whether the inductance is achievable in the space you have.

For a simple single-layer solenoid coil, inductance is approximately:

L = (µ₀ × µr × N² × A) / l

Where:

• µ₀ = 4π × 10⁻⁷ H/m (permeability of free space)
• µr = relative permeability of the core material
• N = number of turns
• A = cross-sectional area in m²
• l = coil length in m

Three things jump out.

First: inductance scales with N². Double the turns, quadruple the inductance. This is why a small nH chip inductor has very few turns (sometimes just a few spirals of metal on a ceramic substrate) and a large H transformer has thousands of turns.

Second: core material matters enormously. Air has µr = 1. Ferrite cores have µr between 10 and 15,000 depending on material. A ferrite-core inductor can achieve the same inductance as an air-core inductor with far fewer turns, which means smaller size and lower DC resistance.

Third: the coil size reference diagram in the calculator is useful for exactly this reason: you can see whether the inductance you’re converting is physically plausible for the coil size you have in mind. A 1 H inductance from a coil the size of a pencil eraser requires a very high-permeability core. A 1 H air-core inductor would need to be much larger.

The bottom line

Inductance conversions are powers of 1,000, same as resistance and voltage. H to mH: multiply by 1,000. mH to µH: multiply by 1,000. µH to nH: multiply by 1,000. Going the other direction, divide by 1,000 each step.

The converter does this in one shot and shows all four units simultaneously.

The practical trap to avoid: the frequency domain tells you what inductance range is reasonable. RF circuits live in nH. Switching supplies live in µH. Audio lives in mH and H. If a converted value lands in a range that feels wrong for the application, it probably is wrong, and the next step is checking whether the input value came from the right datasheet column.